Grouts including water-borne polyurethane binder systems have been developed for the purpose of joining objects, such as tile and masonry, and for filling joints and voids between tiles and masonry. Such grout may be used to join tile to floors, walls, and ceilings and to fill the joints between such tiles so as to join the tiles into a continuous surface. U.S. Pat. No. 7,183,338 (Warren) describes grouts including water-borne polyurethane binder systems and grout products including water-borne polyurethane binder systems are commercially available from Starquartz Industries, Inc. of Baltimore, Md. under the QUARTZ-LOCK® brand.
Grouts including water-borne polyurethane binder systems have many excellent physical properties. Such grouts are strong, durable, and flexible. Grouts are capable of withstanding applied forces and movement of the surface to which the grout is applied, without breaking or cracking. Grouts including water-borne polyurethane binder systems are resistant to staining, both from contaminants and from cleaning solutions and solvents.
While grouts including water-borne polyurethane binder systems are excellent grouts, improvements are possible. For example, in certain grout applications it is desirable to decrease the amount of time required for the grout to harden sufficiently to enable use of the surface to which the grout is applied. Put another way, there is a need in certain grout applications to increase the rate at which the grout cures so that the surface to which the grout is applied can be put into use. Use of the surface would include, for example, the ability of the surface to accommodate foot or vehicular traffic without grout damage or discoloration, or the ability of the grout to be in contact with water or moisture, for example in an exterior application (e.g., an exterior patio or pool deck) or in an interior or exterior high-humidity application (e.g., a shower).
By way of example, it is desirable for a grout product including a water-borne polyurethane binder system to have a compressive strength of about 90 to about 1500 pounds per square inch (psi) before any use of the surface to which the grout is applied. By way of further example, such a grout would be considered essentially fully cured after having developed a compressive strength of about 4000 to about 5000 psi. In certain applications, as many as 48 hours may be required for a grout product including a water-borne polyurethane binder system to develop a compressive strength of about 1500 psi while 21 days may be required for such a grout to develop a compressive strength of about 4000 to about 5000 psi. It would be desirable in certain grout applications to reduce the time required before the grout can be used while at the same time providing adequate time within which to apply the grout.
It would also be desirable to provide grout including other useful properties, such as grouts permitting passage of light therethrough creating, for example, the effect of an appearance similar or the same as the color of the surrounding tile, masonry or other adjacent material. And, it would be desirable to provide a grout which can be formulated to provide improved flexibility, stain resistance and other desirable properties. Acceleration of the rate of grout curing may or may not be desirable in such light-transmissive and other grout formulations and applications.